I just tried this here by creating a new database, with a single table that I could then run your example code against.
I then created a second database and ran Compare between the two, using both V8 and V10.
They both seem to keep the 'N' in front of Auswertegruppennummer:

So I'm not sure why you're seeing it behave differently. Could you let us know some more details as to the collation in use as maybe this is having an effect? Also, can you reproduce the problem by creating a simple example in the same way I did?